SAS and Data Management Kim Magee. Department of Biostatistics College of Public Health

Transcription

1 SAS and Data Management Kim Magee Department of Biostatistics College of Public Health

2 Review of Previous Material

3 Review INFILE statement data bp; infile c:\sas\bp.csv dlm=, ; input clinic $ dbp1 sbp1 dbp2 sbp2; run; Name the dataset you are going to create Import the datafile Give the names of the variables(columns) Indicates the variable in front of it is a character variable

4 Review (cont.) LIBNAME statemnt General Format libname <name of library> "<folder location>"; Example libname class "H:\SASUsersGroup\datasets\"; data class.bp; set bp; run; data bp; set class.bp; run; Create permanent dataset Create temporary work dataset from permanent dataset in library

5 SAS Help Internal Help Press F1 to access Internal Help

6 Questions?

7 SAS Help Online Help

8

9 Missing Data SAS puts. in place of a Missing Value Arithmetic operations with a missing value will result in a missing return value In logical operations missing values are equal to other missing values Missing values are less than non-missing values e.g. when excluding missing data you can use the line below, assuming the value of your data is non-negative Note: when exporting data with missing values to Excel, the missing values will show up as. not blank

10 Formats SAS Formats SAS Format List

11 Formats (cont.) Letters are always character formats Numbers can be either numerical format or character format Be careful when performing equations or merging data that they are in the correct format

12 Formats (cont.) Double click the Column Header in your Data set to see Column Attributes Character Format Numerical Format

13 Numeric Expressions SAS Numeric Expressions

14 Numeric Expressions (cont.) Exercise Calculate BMI using Height and Weight Calculate number of years in the study

15 Numeric Expressions (cont.)

16 Numeric Functions SAS Function ABS(x) Description x EXP(x) FACT(x) x! ee xx LOG(x)/LOG10(x) ROUND(x,unit) Int(x) SQRT(x) MAX(arg-1,arg-2, ) MIN(arg-1,arg-2, ) STD(arg-1,arg-2, ) MEAN(arg-1,arg-2, ) SUM(arg-1,arg-2, ) N((arg-1,arg-2, ) ln(x)/log_10(x) Round x to nearest multiple of unit Round x to nearest integer xx Maximum value of arguments Minimum value of arguments Standard Deviation of arguments Mean of arguments Sum of arguments Counts the number of arguments

17 Numeric Functions (cont.) Exercise Calculate the number of arguments in O1-O5 as O_count Calculate the sum of O1-O5 as P1 Calculate the mean of O1-O5 as P2 Find the minimum value of O1-O5 as P3 Calculate ln(o4) and round to the nearest tenth as P4

18 Numeric Functions (cont.)

19 If-Then/Else Statements Logical SAS expression Then : Statement that is executed if the expression is true Else : Statement that is executed if the expression is false If Then/Else : Statements are nested to produce a series of evaluations Stops once a true statement is encountered More computationally efficient than repeated if statements

20 If Then/Else Statements (cont.)

21 Do End Statements The DO Statement specifies a group of statements to be executed as a unit.

22 Working with Character Variables The Length Statement is a data step statement specifying the internal storage lengths of variables Length can only be set prior to the assignment of values Helpful when merging datasets Variables need to be the same length Syntax: LENGTH variable-1 <$>length variable-n <$>length; $: Specifies the variable is a character type length: number of characters

23 Working with Character Variables (cont.) Using the LENGTH Statement Without the LENGTH Statement

24 Working with Character Variables (cont.) Exercise Create 3 different levels for N1 N1 = (1,2,3,4,5,6)

25 Working with Character Variables (cont.)

26 Character Functions SAS Function Upcase(str)/Lowercase(str) Length(str) Lengthc(str) Strip(str) Tranwrd(str, target, replacement) Catx(delimiter, srt-1, str-2, ) Index(source,excerpt) Scan(str,count) Substr(str,position,n) Description Convert to uppercase/lowercase Length excluding trailing blanks Length including trailing blanks Removes leading and trailing blanks Replaces all occurrences Concatenates variables separated by delimiter Searches sources for excerpt and returns position number Returns the nth character from string Returns n number of characters from str starting at position SAS Character Functions

27 Character Functions (cont.) Exercise Change all titles Mrs. to Ms. Create variable Name with format Last, First Hint: delimiters need around them Create variable AreaCode from TelephoneNumber Create variable State extracted from Address Create an all capitalized variable City

28 Character Functions (cont.)

29 Date Variables SAS Function DATE()/TODAY() DAY(x) MONTH(x) YEAR(x) WEEK(x) DATEPART(x) TIMEPART(x) DDMMMYYYY d Description Returns todays date Returns day of month of date variable Returns month of date variable Returns year of date variable Returns week of date variable Pulls date from Date-Time variable Pulls time from Date-Time variable Creates date variable SAS Date Functions

30 Date Variables (cont.) Formatting Date Variables Internal SAS dates are just a string of numbers. 0 = 1Jan1960 Each day after 1Jan1960 adds 1 Each day before 1Jan1960 subtracts 1 Formatting makes it easier to read Use PUT() function to create new formatted variables SAS Format Date9. Datetime. Time. Description DDMMYYYY DDMMYYYY:HH:MM:SS HHH:MM:SS SAS Date and Time Formats

31 Date Variables (cont.) Exercises Find today s date two different ways Find the current year Create HOUR, MINUTE, and Second variables Use variables created above to create a date-time variable, DTTIME Find TIME using DTTIME Format DTTIME, TIME, TODAY If the subject is still alive calculate when they should have their next visit 60 days from last visit Calculate the number of days between LastContact and TODAY Hint: Try using a DO loop!

32 Date Variables (cont.)

33 Variable Labels Using a LABEL statement in SAS will permanently associate a label with a variable Syntax: LABEL variable-1=label-1 variable-n=label-n;

34 Variable Labels (cont.) Before Label After Label

35 Sub-Setting Data Delete Statement Use the delete statement to exclude subjects with certain observations e.g. delete those with a missing value Output Statement The output statement only includes observations that meet the criteria specified e.g. only include females You can also use the output statement to create individual datasets

36 Sub-Setting Data (cont.) DROP/KEEP Statement Use the DROP statement to get rid of unwanted variables Use the KEEP statement to keep only variables you want If you have a set of variables with same pre-fix that are numbered differently you can lump them all together using : rather than type all out separately

37 Exporting Data Using the Export Wizard Select File» Export Data The window dialog box will appear Select your SAS library libref Library: WORK Select the member of the library Member: Export Click Next

38 Exporting Data (cont.) Export Wizard (cont.) The Select Export Type dialog box will appear Select what data source you would like to export to Most common are *.xlsx, *.csv, and *.txt We will export *.xlsx

39 Exporting Data (cont.) Export Wizard (cont.) Click the Browse button to point to a folder where you want the data saved e.g. save to your H:\ drive

40 Exporting Data (cont.) Export Wizard (cont.) Enter File Name Be sure to scroll down to.xlsx file Default is old version of Microsoft office Click Save Then click OK

41 Exporting Data (cont.) Export Wizard (cont.) Assign a name to the exported table This names the sheet in excel You can be done here and click Finish If you want to save the code click Next Assign a file directory where it will be saved and click Finish It will save a file with code for Proc Export

42 Exporting Data (cont.) Using Proc Export

43 Exporting Data (cont.) Using Proc Export (cont.) Using proc Export to subset data SAS Proc Export

44 Exporting Data (cont.) Using ODS SAS Output Delivery System Gives flexibility in generating reports Great for printing graphs or plots SAS ODS output Tip Sheet